A noise measurement technique, which can acquire microscopic information about ion movements in biological and synthetic membranes has been developed. Fluctuations (noise) in membrane potential or in membrane current during potential control (voltage clamp) are observed in an electrically isolated small patch (10 to the minus 4th power square cm) of squid axon membrane. The noise arises from the spontaneous statistical fluctuations in ion movements in the relatively small number of channels (conducting pathways) in the membrane patch. Fourier analysis of these electrical fluctuations gives relaxation spectra which are related to the potassium ion passage process in the membrane. These measurements will be refined and combined with a stroboscopic technique (noise analysis only during membrane voltage perturbations): 1) To obtain spectra of noise for K ion and Na ion channels in squid and in other membranes, under suitable physico-chemical conditions, to test models of ion conduction which previously could only be applied to macroscopic data. 2) To analyze and expand initial studies of noise in simple synthetic membranes to determine whether these phenomena are pertinent to biological membranes.